Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received March 10, 2017; final manuscript received April 9, 2018; published online May 7, 2018. Assoc. Editor: Gennady Ziskind.

Abstract

In this work, a novel phenomenological model is proposed to study the liquid-to-solid phase change of eutectic and hypoeutectic alloy compositions. The objective is to enhance the prediction capabilities of the solidification models based on a-priori definition of the solid fraction as a function of the temperature field. However, the use of models defined at the metallurgical level is avoided to minimize the number of material parameters required. This is of great industrial interest because, on the one hand, the classical models are not able to predict recalescence and undercooling phenomena, and, on the other hand, the complexity as well as the experimental campaign necessary to feed most of the microstructure models available in the literature make their calibration difficult and very dependent on the chemical composition and the treatment of the melt. Contrarily, the proposed model allows for an easy calibration by means of few parameters. These parameters can be easily extracted from the temperature curves recorded at the hot spot of the quick cup test, typically used in the differential thermal analysis (DTA) for the quality control of the melt just before pouring. The accuracy of the numerical results is assessed by matching the temperature curves obtained via DTA of eutectic and hypoeutectic alloys. Moreover, the model is validated in more complex casting experiments where the temperature is measured at different thermocouple locations and the metallurgical features such as grain size and nucleation density are obtained from an exhaustive micrography campaign. The remarkable agreement with the experimental evidence validates the predicting capabilities of the proposed model.

Figures

Temperature evolution and its first derivative obtained from the DTA of a eutectic solidification process. Identification of the highlight temperatures used for the characterization of the eutectic solidification model.

Temperature evolution and its first derivative obtained from the DTA of a hypoeutectic solidification process. Identification of the highlight temperatures used for the characterization of the hypoeutectic solidification model.

Cubes test microstructures. Experimental measurements and numerical result for microstructural main features (density of nodules and average grain radius) along a profile from the center to a vertex of cubes of 60, 100, 180 mm side.

Return to: A Phenomenological Model for the Solidification of Eutectic and Hypoeutectic Alloys Including Recalescence and Undercooling

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